The invention relates to an apparatus for determining the position of a tool holder and/or workpiece holder.
Devices are known with which the tool holder and/or workpiece holder is pivotably connected by parallel rod kinematic systems to drive units. The parallel rod kinematic systems have rods that are parallel to one another and are connected with their ends movably to the tool holder and/or workpiece holder which is embodied as a supporting platform in the form of a tool center point (TCP) for receiving a workpiece and/or a tool. The parallel rods are movable at their ends in three degrees of freedom whereby depending on the construction one through three of these degrees of freedom are used as positioning axes. The position of the tool holder and/or workpiece holder is not directly determined but indirectly by detecting the position of the drive units. Accordingly, deviations of the position of the tool and/or workpiece holder from the desired position, for example, resulting from deflection forces, acceleration forces or thermal expansion of the rods cannot be detected, so that incorrect machining results.
It is an object of the invention to embody the apparatus of the aforementioned kind such that deviations of the tool holder and/or workpiece holder from the nominal position can be reliably detected.